linux-kernel - Re: [PATCH] I/O space boot parameter

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Date:	Wed, 21 Mar 2007 16:57:59 -0700
From:	Greg KH <gregkh@...e.de>
To:	Daniel Yeisley <dan.yeisley@...sys.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org
Subject: Re: [PATCH] I/O space boot parameter

On Wed, Mar 21, 2007 at 09:37:52AM -0400, Daniel Yeisley wrote:
> On Tue, 2007-03-20 at 13:26 -0700, Greg KH wrote:
> > On Tue, Mar 20, 2007 at 01:25:38PM -0400, Daniel Yeisley wrote:
> > > On Tue, 2007-03-20 at 11:00 -0700, Greg KH wrote:
> > > > On Tue, Mar 20, 2007 at 12:18:24PM -0400, Daniel Yeisley wrote:
> > > > > It has been mentioned before that large systems with a lot of PCI buses
> > > > > have issues with the 64k I/O space limit.  The ES7000 has a BIOS option
> > > > > to either assign I/O space to all adapters, or only to those that need
> > > > > it.  A list of supported adapters that don't need it is kept in the
> > > > > BIOS.  When this option is used, the kernel sees the BARs on the
> > > > > adapters and still tries to assign I/O space (until it runs out).  I've
> > > > > written a patch to implement a boot parameter that tells the kernel not
> > > > > to assign I/O space if the BIOS hasn't.  
> > > > 
> > > > How prelevant are machines like this?  And why are the BARs on these
> > > > devices wrong?
> > > > 
> > > I don't have any sales numbers, but I can tell you that our current
> > > systems can have up to 64 PCI buses.  
> > > 
> > > I've been working with Emulex cards, and my understanding is that the
> > > BARs on the devices aren't wrong, but we can't allocate 4k of I/O space
> > > for each one.  So we maintain a list in the BIOS of devices that don't
> > > actually need I/O space and then don't assign it.  I've tested an a
> > > x86_64 system with 20+ adapters and saw all the disks attached without
> > > any problems.
> > 
> > Ah.  Others are working on providing a fix for this too, but it is being
> > done in the drivers themselves, not in the pci core.  Look in the
> > linux-pci mailing list archives for those patches (I don't think they
> > every went into mainline for some reason, but I might be wrong...)
> > 
> > I suggest you work with those developers, as they have the same issue
> > that you are trying to solve here.
> > 
> 
> I have seen some patches that make the drivers I/O port free here:
> http://lkml.org/lkml/2006/2/26/261

Ah, yes, those are the ones.

> I checked and they still aren't in the mainline.  

Poke the developer to get them there :)

> I don't know that it matters though because I see all the disks attached
> to the system regardless of whether or not the adapters get I/O space.
> The real issue I have is with all the error messages I get at boot.  I
> see 40+ messages that say "PCI: Failed to allocate I/O
> resource..." (from setup-res.c) when the kernel tries to allocate the
> I/O space and can't.  The modules load fine.  I see all the disks just
> fine.  But that many error messages tends to raise concerns and causes
> support calls from customers.

If this isn't an issue for functionality, why not fix your BIOS then?

And doesn't the above linked patch set also solve your issue with the
noise in the syslog?

thanks,

greg k-h
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